Integrated circuits may be implemented using analog and/or digital circuits. To increase performance, the integrated circuits are typically made using a fabrication process having a minimum feature size for a target cost and speed. Using the minimum feature size generally reduces power consumption.
Different processes require different voltage supply levels to provide operation at a given clock frequency. For example, for a predetermined clock frequency, a 0.15μ process may require 1.5 V, a 0.13μ process may require 1.2 V, and a 0.09μ process may require 1.0 V. In conventional integrated circuits, the individual analog circuits generally need to be redesigned when the process is changed. The redesign process adds additional cost and delay to the design process.
Referring now to FIGS. 1A and 1B, an integrated circuit 20 in FIG. 1A fabricated using Process A and includes analog circuits 1, 2, 3, 4, 5, . . . and X as shown. An integrated circuit 20′ in FIG. 1B has the same functionality, is fabricated using Process B and includes analog circuits 1′, 2′, 3′, 4′, 5′, . . . and X′, which are redesigned versions of the corresponding circuits in FIG. 1A. Since Process A is faster than Process B, a power supply 22 in FIG. 1A generates V1 will typically be less than V2 (which is generated by power supply 22′ in FIG. 1B) for a given clock frequency.
Referring now to FIG. 2, a first process is used to implement an inverter 30 that is commonly used in analog circuits. Vdd is required to provide a predetermined switching speed, which refers to the time required for the output Vout to transition when the input Vin transitions. When a second process that is slower than the first process is used, Vdd is increased to obtain the predetermined switching speed. When a third process that is faster than the first process is used, Vdd is decreased to obtain the predetermined switching speed.